1. Field of the Invention
The present invention relates to a keyboard device for use in a keyboard musical instrument such as an electronic piano.
2. Description of the Related Art
A keyboard musical instrument is known which is structured such that a keyboard section provided in a musical instrument case is openably and closably covered by a keyboard lid having a front lid and a rear lid foldably coupled together with a coupling section, as described in Japanese Patent Application Laid-Open (Kokai) Publication No. 2009-145711.
An open and close device for the keyboard lid of this type of keyboard musical instrument includes a front guide shaft that is provided on the front portion of the front lid and projects toward sides of the front lid, a displacement mount section that is provided on the front portion of the rear lid and resiliently displaced in a vertical direction, a rear guide shaft that is mounted on the displacement mount section and projects toward sides of the rear lid, and a common guide groove that guides the front guide shaft and the rear guide shaft in a forward and rearward direction of the musical instrument case.
On the front portion of the common guide groove, a drooping portion is formed, drooping downward from above the front side of the keyboard section. Immediately before the keyboard lid is completely closed, the front guide shaft is guided by the drooping portion. As a result, the front portion of the keyboard section is covered and hidden.
In this open and close device of the keyboard lid, the front guide shaft and the rear guide shaft are inserted into the common guide groove to be guided. Thus, when the keyboard lid is opened or closed, the front guide shaft and the rear guide shaft are both guided by the common guide groove. Accordingly, both of the guide shafts can be moved by using one guide groove.
Immediately before the keyboard lid is closed, the front guide shaft is guided by the drooping portion of the common guide groove to make a drooping movement.
Accordingly, the rear guide shaft also similarly makes a drooping movement. However, the common guide groove guiding the rear guide shaft does not have a drooping shape for letting the rear guide shaft to make a drooping movement. Therefore, a structure for absorbing a drooping movement amount of the rear guide shaft is required.
For this purpose, in the structure disclosed in Japanese Patent Application Laid-Open (Kokai) Publication No. 2009-145711, the displacement mount section for absorbing the drooping movement amount is provided to let the rear guide shaft to make a drooping movement. Immediately before the keyboard lid is closed, the displacement mount section is displaced in the vertical direction by the weight of the keyboard lid to cause the front lid and the rear lid to be placed on a same plane.
However, since this open and close device of the keyboard lid is structured so that the front guide shaft and the rear guide shaft are inserted into the common guide groove to be guided. If the displacement mount section for displacing the rear guide shaft of the rear lid in the vertical direction with respect to the rear lid is not provided, the keyboard lid is bent by the rear portion of the front lid and the front portion of the rear lid being lifted and therefore the front lid and the rear lid cannot be placed on the same plane when the keyboard section is covered and closed by the front lid and the rear lid.
Therefore, there is a problem in this open and close device of the keyboard lid in that the structure is intricate and complex and, when the front guide shaft and the rear guide shaft are guided by the common guide groove, the rear lid is resiliently displaced by the displacement mount section in the vertical direction, whereby the open and close movements of the keyboard lid become unstable.